Reaching adulthood certainly takes longer than it did a generation ago, but new research shows one way that parents are contributing to the delay. A national study found that college students think 25 years old is the "right age" to get married, while a majority of parents feel 25 is still a little too soon. So it's no coincidence that when Justin Bieber said he'd like to wed by 25, Oprah Winfrey urged him to wait longer.